DESCRIPTION OF THE PESTS

Cutworms are only occasional pests of high desert and Central Valley
alfalfa but are frequent pests in the low desert where alfalfa is planted on
beds. The granulate and the variegated cutworms are the two species that most
commonly attack low desert alfalfa.

Female moths lay white or greenish eggs in irregular masses on
leaves or stems of plants, often near the base of the plant. Eggs darken as
they approach hatching. Full grown
caterpillars are
about 1.5 to 2 inches long and appear as smooth-skinned caterpillars of various
colors and patterns. Larvae frequently roll into a C-shape when disturbed.
Cutworms feed at night and hide during the day in soil cracks and under debris
and loose soil.

DAMAGE

In the Central Valley, variegated cutworm populations may develop in
weedy areas and migrate into seedling stands or occasionally mature stands.
Injurious populations usually occur from April to late June. Seedling alfalfa
stands can be severely damaged by cutworms cutting the seedlings off at or just
below the soil surface.
Established fields are damaged when cutworms cut off new growth or feed
on the alfalfa foliage.

Granulate cutworm is a devastating pest of bed-planted alfalfa
and can also be a pest of alfalfa planted between borders. Low desert alfalfa
fields are attacked from May through October, but the pest occurs year round in
fields. Established alfalfa fields can be severely injured when cutworms cut
off new shoots at or below ground level following harvest. The pest often goes
undetected after cutting and hay removal but the problem becomes apparent when
the field is irrigated and there is little or no regrowth.

MANAGEMENT

Tillage, flood irrigation, and weed control are important in cutworm
management. When damage is severe in seedling fields, apply an insecticide
bait.

Cultural Control

Tillage helps to limit cutworm populations; seedlings in well-tilled
fields—especially when there is an interval between crops—are less likely to
have cutworm problems. Keep the field and field edges weed-free. Flood
irrigation can drown many cutworm larvae. Flood irrigation during the day will
attract many birds that prey on the cutworms as the advancing water forces
larvae from hiding.

Organically Acceptable Methods

Cultural controls are acceptable for use on an organically certified
crop.

Monitoring and Treatment Decisions

Cutworm infestations are sporadic, and treatment guidelines have not
been established in California. Check for cutworms by looking under duff and
carefully digging to a depth of 1 inch in loose soil near alfalfa crowns. When
cutworm numbers exceed one or two per foot of row or severe damage is apparent,
it may be necessary to treat. If treating with baits, apply baits in late
evening or at night when cutworms are on plants.

Common name

Amount/Acre**

R.E.I.+

P.H.I.+

(trade name)

(hours)

(days)

The following materials are listed in order of
usefulness, taking into account efficacy and impact on natural enemies and
honey bees. When choosing a
pesticide, also consider environmental impact. Not all registered pesticides are listed. Always read label of product being used.

A.

PERMETHRIN*

(Pounce) 25WP, 3.2EC, WSB

Label rates

12

14

(Ambush) 25WP

8.2–12.8 oz

12

14

MODE
OF ACTION: A pyrethroid (Group 3)1 insecticide.

B.

CYFLUTHRIN*

(Baythroid) 2E

0.8–1.6 fl oz

12

7

(Renounce) 20WP

1–2 oz

12

7

MODE OF ACTION: A pyrethroid (Group 3)1
insecticide.

C.

LAMBDA-CYHALOTHRIN*

(Warrior)

1.92–3.2 fl oz

24

7 – hay; 1 – forage

MODE OF ACTION: A pyrethroid (Group 3)1
insecticide.

COMMENTS: Do not apply when bees are actively foraging. Do not apply more than 0.24 pt/acre/cutting or 0.96 pt/acre/season.

D.

INDOXACARB

(Steward) 1.25 SC

6.7–11.3 fl oz

12

7

MODE OF ACTION GROUP NUMBER1: 22A

COMMENTS: Make no more than one application per cutting. Not
for use in alfalfa grown for seed or for sprouts for human consumption. Do not apply more than 45 fl oz/acre/crop season.

**

See label for dilution rates.

+

Restricted entry interval (R.E.I.) is the number of hours
(unless otherwise noted) from treatment until the treated area can be safely
entered without protective clothing.
Preharvest interval (P.H.I.) is the number of days from treatment
until the field can be grazed or cut.
In some cases the R.E.I. exceeds the P.H.I.; the longer of these two intervals is the minimum time that must elapse before harvest may take place.

*

Permit required from county agricultural commissioner for purchase or use.

1

Modes of action are important in preventing the development
of resistance to pesticides. Rotate chemicals with a different mode-of-action
group number, and do not use products with the same mode-of-action group
number more than twice per season.
For example, the organophosphates have a group number of 1B; chemicals
with a 1B group number should be alternated with chemicals that have a group
number other than 1B. Mode of action is assigned by IRAC (Insecticide
Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.